Undefined function from static library

0
votes

I am trying to build a static library using MinGW.

Everything was going fine until I tried to use the library and got an error saying that add_numbers is an undefined function.

Many other people have had this problem and sorted it out by moving their library to be linked after the source files were included, but that was how I had written my batch file anyway, so that was not of much help.

Here are my sources.

mylib.h

#ifndef MYLIB_H
#define MYLIB_H
int add_numbers(int a, int b, int c);
#endif

mylib.c #include "mylib.h" int add_numbers(int a, int b, int c) { return a+b+c; }

I'm building my .a file with the following commands

gcc --std=c89 -c mylib.c -o mylib.o

ar rcs libmylib.a mylib.o

I've also tried with out specifying the standard. There are no errors or warnings when running this command.

Next, my test program looks like this.

#include <stdio.h>
#include "mylib.h"
int main()
{
printf("The sum of 1, 2, and 3 is %d", add_numbers(1, 2, 3));
getchar();
return 0;
}

And lastly, we build the test with this command. gcc mylibtest.c -L -lmylib -o test.exe

I've tried moving around those commands into many many different sequences, but always receiving the following error:

C:\Users\Aaron\AppData\Local\Temp\cc0ERpBi.o:mylibtest.c:(.text+0x26): undefined reference to `add_numbers' collect2.exe: error: ld returned 1 exit status

E:\my_first_static_library>

Any help would be very appreciated, I've read every tutorial I could find on the art of writing static libraries, as well as a good ten stackoverflow questions.

1
gcc
yugr has your answer. You have -L instead of -L., so the the linker finds that the argument of -L is -lmylib, i.e -lmylib is the name of a directory you want the linker to search for libraries and consequently doesn't find that you're actually linking any libraries. Hence undefined reference to your library function. - Mike Kinghan

1 Answers

1
votes

You are missing a dot after -L:

gcc mylibtest.c -L . -lmylib -o test.exe